The constant potential oxidation of adlayers of CO on a bead type Pt(111) electrode created by the impinging jet flow technique has been studied in 0.5 and 0.05 mol dm(-3) H2SO4 electrolyte. Washing procedures were developed which allowed work to be carried out for long periods of time without contamination problems. At low potentials (<680 mV vs. RHE) in 0.5 mol dm(-3) H2SO4 the compact adlayers were slowly oxidized in a process which first involved a constant current plateau followed by a single symmetric peak. The total oxidation charges of the transients corresponded to that of a compact CO adlayer and the peak charges to that calculated from data reported in the literature for a looser adlayer structure. In 0.05 mol dm(-3) H2SO4 the adlayers oxidize much faster and the oxidation process is more complex. The current - time traces for the stronger electrolyte were described well by an equation especially derived for the oxidation kinetics under the particular conditions used in this work. Values for a potential dependent rate constant for the oxidation were determined by means of curve fitting.